Why is it that so many baby names sites have different meanings for the same name?

Like baby name books and babynames.com and other sites seem to have different meanings. ---On babynames.com i was searching the name 'Shana' and it says on their the meaning is ''God is gracious'' and that the Origin was American. --But when i looked at a babyname book at the library it says the name means 'Beautiful' and that it's Hebrew. --And i even typed in google and 3 sites so far say it's believed to be hebrew and mean Beautiful One said it was american but meant Beautiful... Is babynames.com not correct or what?Why is it that so many baby names sites have different meanings for the same name?
Different languages have similar names that have different meanings in other languages. For example, the Latin meaning of Jacob is supplanter. However, the Hebrew meaning is deceiver because of the biblical story of Esau and Jacob. Also, sometimes these names don't translate perfectly. The name Meredith is a perfect example of this. Meredith comes from the old Welsh male name Mareludd, which probably means 'great lord'. The second element '-iudd' means 'lord'; the first element probably means 'great', or maybe 'sea'. This means that the meaning of the name Meredith could be great lord or sea lord.Why is it that so many baby names sites have different meanings for the same name?
like everything has more than one meaning?